This invention relates generally to tracking the position of objects in three dimensional space, and more particularly to verifying the position of components of an object in 3-D space using a probe apparatus.
In many assembly processes of electronic devices, several different components must be assembled quickly and reliably to allow the devices to be offered to consumers at low prices. Circuit boards used in electronic devices are one of the most common multi-component parts that require such efficient assembly. Assembling printed circuit boards, often called "stuffing" the circuit board, typically involves placing components on a circuit board in predetermined locations and soldering the components in place. The components might include resistors, capacitors, integrated circuits, op amps, connectors, wire leads, clock crystals, inductors, or a variety of other passive and active components. Many different types of these components are often assembled on a single board and must be soldered in the correct location on the board for a board to function properly. The components can be placed and soldered by human assemblers but are more often "stuffed" by more automated methods. For example, a "pick and place" machine is a robotic device that automatically puts the various components in previously programmed positions. A "wave solderer" is a machine that solders many components on a circuit board in place at once. These types of tools greatly accelerate the circuit board assembly process.
Regardless of how a board is assembled, by hand or by machine, it is often important to perform quality control measures to ensure the board has the proper components in the proper locations. A board with even one component in the wrong place may function incorrectly or not at all. Errors in the assembly process can originate from a variety of sources. For example, a human assembler might have put a component in the wrong position on the circuit board. Or, a human operator might have loaded the wrong components in a pick and place machine. In many cases, different components appear very similarly and may vary only by their values or class. For example, resistors having different resistance values or capacitors having different capacitance values may appear almost identical, leading to these errors. Or, the pick and place machine may have been incorrectly programmed, leading to other errors. Regardless of why the errors occurred, the result is the same: an incorrectly placed component can result in a non-functional product. The more non-functional products resulting in an assembly process, the greater the cost of the functional products to the buyer.
Quality control procedures for circuit boards are rigorous processes in which every component on the circuit board is checked to ensure that the board has been properly assembled. Both the type of component and also the specific values of the components are checked. This is often accomplished by human operators who visually inspect the circuit boards. The process involves looking at a document, usually a "bill of materials" and/or a board schematic, and confirming visually that every component on the board is correctly placed and has the correct value. This process tends to be tedious because it involves looking back and forth from the board to the documents. What is needed is a rapid way to point at a position or a component on a physical circuit board and a system that immediately reports the type and value of the proper component that is supposed to be located at the pointed position, without the operator having to look at a long list or a dense schematic drawing.